1. Pole Top Extension Bayonets
In the utility industry, pole top extensions or bayonets are frequently used to add length to the top end of wooden utility poles. Pole top extensions are typically used to increase the height of a wooden utility pole, for example, for mounting existing wires at a greater height above ground level when wire or cable requirements change. The pole top extension eliminates the need to resort to replacing or changing out the entire wooden utility pole.
Many states have code requirement which mandate that electrical lines must be positioned above television cables. Rather than incur the costs of burying the TV cable or duplicating the poles used, therefore, it is often desirable to mount television cables to existing utility poles. Ground clearance problems usually will not permit simply mounting a television cable below the electrical lines.
Accordingly, the choice will be between adding a pole top extension to the existing poles and raising the electrical lines, or changing out the existing poles for taller poles which can support both lines.
Changing out poles is an expensive procedure since it usually must be done without interrupting existing service. Moreover, changing out poles is environmentally undesirable in that it results in the use of new pole timbers in substantial numbers.
Moreover, as new utility lines are added to utility poles for any reason, at some point the existing cross-arms cannot be used to support the lines and new vertically spaced cross-arms are required. Moreover, with additional line often comes auxiliary equipment, and particularly heavy transformers. Thus, utility pole extensions can be used for the additional lines, but most pole top extension bayonets are not rated for transformers and other heavy equipment.
Finally, utility lines can be reconfigured to provide corner runs, where the direction of line travel changes (typically by 90.degree.), causing transverse stresses tending to topple the pole. Guying frequently required at corner runs and some pole top extensions are not rated for guying. Thus, one of the important considerations when deciding whether or not to add a pole top extension or change-out a pole has been whether or not guying is required or transformers must be installed on the extension. While pole top extensions for utility poles have been in use for many years, many are not rated for support of anything other than a cross-arm and wires. Thus, in line reconfigurations requiring guying or heavy equipment support, the only acceptable approach often has been to change out the poles.
2. Specific Prior Art Systems
While the desirability of using pole top extensions has been around for many years, the solutions have not been very satisfactory. The patent literature contains various approaches which have not gained wide-spread use. For example, U.S. Pat. No. 1,420,430 to Jaeckle and Mehlhorn discloses a means for securing the sections of a mast or pole together. Specifically, this is done by using a plurality of curved plates which are placed symmetrically around the pole and are bolted to the pole. These plates are secured so as to overlap the abutting ends of the two sections of the mast or pole to be held together. Owing to the elasticity to the plates, they may be employed to connect poles of somewhat different diameters; however, this apparatus is not typically suitable as a pole top extension due to the often large difference in diameters between the existing pole and the extension bayonet. Furthermore, Jaeckle and Mehlhorn's device is designed to connect two circular cross-section pole lengths together, and could not easily join a circular cross-section pole to a rectangular cross-section extension bayonet.
U.S. Pat. No. 3,201,834 to Baittinger and U.S. Pat. No. 3,802,206 to Moore, et al. disclose pile splicers for joining lengths of timber piles. These devices are not designed as pole top extension bayonet connectors. Furthermore, these devices are not well suited to join two piles of differing cross-section.
U.S. Pat. No. 4,032,244 to Quayle discloses a pole top extension bracket for a wooden utility pole. A bracket is mounted between the flattened top of a utility pole and the bottom end of an extension bayonet. A center shaft extends from this bracket to be received within a central bore provided in the utility pole, the extension pole or both. A number of threaded fasteners and straps run longitudinally across the connection between the pole and extension bayonet, and are bolted onto the exterior of both. These fasteners and metal straps are evenly spaced at four locations around the circumference of the poles. U.S. Pat. No. 4,097,165 to Quayle represents a slightly altered form of this design. The design of both of these Quayle devices could only be used to connect two poles of circular cross-section, and not one of circular cross-section to one of rectangular cross-section and the Quayle brackets assemblies are complex in the extreme. The time required to install such assemblies on the top of a utility pole would be unacceptable for wide-spread use.
U.S. Pat. No. 4,048,779 to Valenziano, et al. discloses a turn buckle connector which is used in replacing an existing utility pole without disturbing the hardware that is mounted thereon. The free end of the existing utility pole with the hardware mounted thereon is severed from the existing pole. A new pole is placed into the earth with its end then connected to the turn buckle which has a plurality of girdle plates each having side marginal flanges and a terminal flange. The turn buckles connect the side marginal flanges of the adjacent girdle plates to each section to draw them toward them together so that the section is gripped. This turn buckle comprises a plurality of girdle plates having radially projecting flange portions cooperating to form a radially projecting flange. The Valenziano turnbuckle is specifically designed for use in replacing the bottom section of a utility pole, rather than the top section. This obviously has the undesirable requirement that the existing pole bottom be removed from the ground and the further requirement that the extension must be very large in order to withstand the entire weight of the pole. Furthermore, this device is specifically designed to only connect together two poles having circular cross-sections.
U.S. Pat. No. 4,092,079 to Swanson discloses a connector for replacing an existing utility pole without disturbing the hardware mounted thereon. Accordingly, it again is based upon removal of the bottom of the pole, with the above-noted disadvantages. The Swanson connector includes an annular sleeve engageable about the outside of the new pole section. This sleeve projects above the bottom end of the Swanson existing pole section and below the-top end of the new utility pole, forming a socket for receiving both of these ends, with push plates positioned within the sleeve to embrace the top section to hold it socketed therein. These push plates are engaged with the pole sections by means of bolts anchored in the sleeve. This device is not suited for connecting an extension to the circular top end of a wooden utility pole having its cross-arms in place because the cross-arms would interfere with the sleeve.
U.S. Pat. No. 5,222,344 to Johnson discloses a pole for supporting utility lines. In this structure, an interior lattice of composite members forms an elongated open celled beam which is enclosed by a composite outer skin. The interior lattice is made of protruded composites designed to replace steel in some applications where their weight corrosive resistance and insulated properties are useful. The Johnson structure, in one embodiment, shows the exterior skin forming a sleeve over the top of a post thus forming a pole top extension. The Johnson device is not directed at a method or apparatus of connecting an extension to an existing pole, but rather the manufacture or fabrication of a utility pole.
Rather than employing assemblies as set forth in the above patent art, the industry has tended to use one of two approaches, namely, to bolt and band together a pair of extension members to opposite sides of a pole or install a fiberglass extension tube to the top of the pole.
Typical of the bolt-together approach is the assembly of Pacific, Gas & Electric Engineering Standard No. 028691. In this assembly, two rectangular wooden extension members are bolted to the opposite sides of a cylindrical wooden utility pole. A bracket is also lag screwed into the pole and bolted to both of the extensions. Finally, a cross-arm assembly is bolted to the top ends of the extension members.
This bolt-together assembly, however, is very tedious to install, typically requiring one to two hours for two line men on the pole and/or in a hoist to construct the assembly on the pole top. While it is rated for guying, transformers cannot be supported on such pole top extension members. This is due to the fact that the weight of these pole top extensions, and any fixtures attached thereto, is supported fully by only one bolt positioned at a bottom bracket. This bolt passes through the utility pole, and is subjected to heavy shear stresses as a result of the weight of the extension bayonet assembly.
A fiberglass pole top extension of the type in use in the industry for 20 years is shown in the publication entitled "Highline Case History Fiberglass Utility Poletop Extensions" and Tech Data Sheets of Highline Products Corporation of Old Saybrook, Conn.
In this design, a hollow fiberglass extension pole, having a circular cross-section, is mounted onto the top of a metal extension bracket which is attached to the top of a cylindrical utility pole. The fiberglass extension is attached by mounting it slidably over an upwardly protruding bracket collar. Numerous limitations exist with this device. First, the use of hollow fiberglass, as opposed to wood, results in an extension bayonet which is much weaker than a wooden extension. The fiberglass tube is not being able to withstand any significant bending stresses that would be caused, for example, by guying or by mounting a heavy transformer onto the bayonet extension. As such, these fiberglass extension bayonets are typically limited to carrying only cross-arms and attached wires. Secondly, the drilling of holes in the fiberglass bayonet is difficult in the field. Clean drilling of tubular fiberglass extensions can best be accomplished in a factory using carbide drills which are not normally available in the field. Consequently, fiberglass extension bayonets typically are special ordered from a factory for later use in the field. The alignment of field-drilled holes when mounting the bayonet is also difficult. This may cause problems with the proper orientation of components, such as wires and cross-arms mounted onto the bayonet extension. Thirdly, the fiberglass collar used has a height less than its diameter, which is adapted to receive only a single transverse lag bolt therethrough. The resulting structure is thus not very resistant to bending stresses. Lastly, users of the pole top extensions sometimes do not know the relationship between the mounting bracket and the drilled holes. Consequently, this requires additional holes to be drilled into the bracket in order to allow the user to rotate the pole top extension 90.degree. if necessary.
Numerous other problems exist with fastening cross-arms to a cylindrical shaped extension bayonet. There will be only a minimal point contact occurring when a flat sided cross-arm is bolted to this cylindrical shaped face. This problem lowers the stability of the connection. Consequently, under heavy wind loading, cross-arm connections to fiberglass extensions tend to wobble and loosen with time.
Furthermore, tubular extension bayonets are also particularly ill-suited for use as corner run assemblies where the lines change their direction of travel. This is due to the fact that it is difficult to attach two perpendicular cross-arms at about the same height on the sides of the bayonet. The use of two perpendicular cross-arms is a common assembly for corner run poles where the lines change their direction of travel. Typically, at these corner end runs, a second cross-arm is mounted lower than, and perpendicular to, a first cross-arm. The lines are simply dropped down from the ends of the first cross-arm to the ends of the second cross-arm and then proceed away in a direction of travel perpendicular to that from which they arrived. Dropping these lines down from the first cross-arm to the second perpendicular cross-arm uses up considerable vertical space on the extension bayonet. As a result, it is not possible to carry transformers or other heavy equipment at these corner run locations as this heavy equipment would also require considerable vertical space on the extension bayonet. Existing extension bayonets simply do not have the sufficient vertical space or strength to support both heavy equipment and two perpendicular cross-arms.
3. Objects of the Invention
The main object of the present invention is to provide an apparatus for connecting a pole top extension to the top end of a cylindrical wooden utility pole which will provide a high strength pole extension capable of being guyed and loaded with heavy equipment, such as a transformer.
It is a further object of the invention to provide a wooden pole top extension such that, when a pole top has become sufficiently weathered or decomposed, replacement can be made of this top section of the wooden utility pole without the need for replacement of the entire wooden utility pole.
Another object of the present invention is to provide a pole top extension to which cross-arms can be more easily mounted in the proper aligned orientation particularly in corner runs where the direction of travel of the lines changes, typically by 90.degree.. Specifically, it is an object of the present invention to provide a pole top extension to which parallel cross-arms can be mounted at the same height, without using up significant vertical height on the extension bayonet.
Another object of the invention is to provide a pole top extension that can be guyed from any one or all four sides.
Another object of the present invention is to provide a pole top extension which is more easily installed by allowing for the assembly of all cross-arms, transformers and guying hardware onto the extension bayonet while the bayonet is on the ground. This then enables the resulting unit to be raised as a whole for attachment onto a position on top of the wooden utility pole.
Another object of the invention is to provide a pole top extension wherein one or more cross-arms can be securely mounted such that they will not wobble excessively under heavy wind loads, with the cross-arms readily mounted either parallel or perpendicular to one another when a plurality of cross-arms is mounted to one pole top extension.
Another object of the invention is to provide a pole top extension wherein the collar connecting the extension bayonet to the assembly has a sufficient height to width ratio such-that it extends far enough to cover a sufficient length of the bottom of the extension bayonet such that the connection produced is able to withstand considerable bending stresses.
It is another object of the invention to provide a pole top extension that can be mounted onto the flattened top of a wooden utility pole, without requiring first for the removal of any existing cross-arms already mounted to said utility pole.
An additional object of the invention is to provide a pole top extension which, during installation, does not require first orienting an assembly mounted on top of a wooden utility pole followed by secondly orienting the direction of an extension bayonet.
The apparatus and method of the present invention has other objects and features of advantage which will become apparent from and are set forth in more detail in the Description of the Best Mode of Carrying Out the Invention and the accompanying drawing.